Long-term and high dose dexamethasone injection decreases the expression of Immunoglobulin Heavy (Light) Chain Variable Region Genes (IGH(L)Vs) in the mouse spleen.

Glucocorticoid hormones have been widely used in clinical practice as potent anti-inflammatory and immunosuppressive agents. However, the underlying mechanisms of how they work remain unaddressed. Here, we used RNA-set to profile spleen gene expression in adult mice after consistent intraperitoneal injection of dexamethasone. We identified 13565 genes in control (injected with 0.9% NaCl) and 13702 genes in dexamethasone-injected group, 12920 genes were expressed in both, but 645 genes were identified only in control and 782 genes were identified only in the dexamethasone group. In the dexamethasone-injected group 101 and 67 genes were down-and up-regulated, respectively. Among these, 129 were coding genes, 19 were identified as non-coding genes or pseudogenes, and the remaining 20 were TEC (to be experimentally confirmed) genes. Gene ontology (GO) and KEGG pathway analysis revealed that the cytokine-cytokine receptor interaction pathway was highly enriched in these differentially expressed genes, and that a majority of the 129 identified coding genes were involved in immune system and cell adhesion-associated processes. Moreover, systemic lupus erythematosus, renin-angiotensin system, fat digestion and absorption, and glycerolipid metabolism pathways were significantly affected in the dexamethasone-treatment group. No obvious signaling pathway was enriched in the control group. Additionally, 20 immunoglobulin heavy or light chain variable region genes (IGH(L)Vs) were down regulated in the dexamethasone-injected group. IGH(L)Vs encode the variable region of immunoglobulin heavy chain and determine the diversity and specificity of antibodies. We were unable to determine the function of the 19 non-coding genes with differential expression following dexamethasone treatment. Our findings indicate that the expression of IGH(L)Vs and non-coding genes play an important role in the anti-inflammatory and immunosuppressive effects of dexamethasone and could be developed as potential agents in clinical practice.